The Political Functions of Smiles by Kamala Harris and Donald J. Trump During the 2024 Presidential Debate

Smiles are arguably the most primal of political activities. By signaling largely prosocial intent, they lubricate social interactions, providing the basis for group formation and interpersonal expectations. However, smiles are not monolithic behaviors. They can be characterized by the muscles involved, how strongly they are contracted, and their timing. Furthermore, context influences both the likelihood of smiles occurring and how they are interpreted. Here, we characterize four basic smile types (Reward, Affiliative, Dominance, and Fear) as serving the social functions of broadening-and-building coalitions and maintaining-and-managing hierarchies, respectively. To better understand the relationship between political leaders and the intent of their smiles, especially in the United States, we content analyze the only 2024 presidential debate between Vice President Kamala Harris and ex-President Donald Trump, utilizing two Facial Action Coding System-certified coders to identify the presence and types of smiles displayed. Findings suggest there are distinct differences in candidate smile production potentially due to political identity.